#define _CRT_SECURE_NO_WARNINGS 1

int missingNumber(int* nums, int numsSize) {
    int sum = 0;
    for (int i = 0; i < numsSize; i++)
        sum ^= nums[i];
    for (int i = 0; i < numsSize + 1; i++)
        sum ^= i;
    return sum;
}